The application of cathodic-arc-deposited films has been very slow due to the infamous macroparticle problem. We report about the application of the open Twist Filter as the key component to an advanced filtered cathodic arc system. Ultrathin tetrahedral amorphous carbon (ta-C) films have been deposited on 6 inch wafers. Film properties have been investigated with respect to application in the magnetic data storage industry. Films can be deposited in a reproducible manner where film thickness control relies on arc pulse counting once deposition rates have been calibrated. Films of 3 nm thickness have been deposited that passed acid and Battelle corrosion tests. Monte Carlo Simulation of energetic carbon deposition shows the formation of an intermixed transition layer of about 1 nm. The simulation indicates that because the displacement energy of carbon is not smaller than of magnetic materials, films thinner than 2 nm are either not high in sp(3) content or represent a carbidic phase, i.e. contain substrate material. The last finding is general and not limited to cathodic arc deposited ta-C films.